The subject matter described herein relates generally to wind farms and methods for operating the wind farms, and more particularly, to methods for operating the wind farm in a reserve power mode.
Generally, a wind turbine includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Often, several or a plurality of wind turbines form a wind farm in which the total produced power of the wind turbines is controlled by a supervisory or subordinate control system of the wind farm. Modern wind farms may have a very high installed electrical power, in particular if the wind farm is positioned at locations offering particularly good wind yields, such as at the coast or off-shore, and/or if the wind farm includes a larger number of modern wind turbines. The connection of high power wind farms to a grid may pose challenges regarding grid quality, in particular if the percentage of the power fed by wind farms into the utility grid increases. In this respect, energy suppliers and energy traders, respectively, may require an appropriate behavior of the wind farms in particular during an instability of the grid, e.g. a frequency shift, and/or during an increasing power demand in the grid. For example, the wind farm may be required to operate in a reserve mode in which the wind farm produces less power than possible in order to be able supply extra power when needed. However, this reduces the annual yield of the wind farm.
It would therefore be desirable to provide systems and methods allowing for flexible and reliable operating of wind farms in reserve mode.